the concussion she suffered is expected to prevent mrs. clinton from appearing this week before two congressional committees looking at the attack in benghazi, libya that killed four americans including the u.s. ambassador. south africa says that former president nelson mandela underwent surgery for gallstones yesterday. the operation on the 94-year-old was described as successful. now today's weather, rain is likely east of the mississippi and along the west coast. there they are also bracing for snow. the week ahead will start with scattered storms, and will end with the official start of winter. ,,,,,,,, ,,,,,,,,,, >> osgood: friday's awful events in newtown, connecticut bring back some all too familiar questions. how could this have happened? and what can be done? here is martha tischner. >> caller is indicating that she thinks someone is shooting in the building. >> reporter: somehow the idea that little children had been shot made it worse. >> we heard a lot more than, the ambulance came, then the policemen told us to run out of the